Group, rank and replace

Morning,

I've attached a sample dataset, There's a few things I need it to be able to do:

-I want to be able to rank them by SALES ORDER

-Once ranked, I want to be able to show the names of the first 5, but anything after that replace with 'Other' and aggregate their number.

-I then need to show the Average failure % for the Top 5 SALES ORDER and Other.

-This needs to be dynamic based on selections e.g. Period.

So I end up with something looking like this (These aren't the correct number)

Thanks